Purple Loosestrife

Purple Loosestrife

(Wilson)

Purple Loosestrife (Lythrum salicaria) is a plant species native to Europe, Asia, Northwestern Africa, and Southeastern Australia. It made its way over to the United States in the 1800s and has been plaguing Vermont for many years. It grows very rapidly, reaching heights of 1-1.5 meters, forming vast colonies. Each root can produce 30-50 stems which create a web that chokes out competitors. It was brought over here as a medicinal herb for treating diarrhea and dysentery. Its bright purple flower also attracted people to use it as an ornamental. Unfortunately it spread like wildfire, mainly in wetland areas. It is distributed by wind and water, disrupting the water flow of rivers. It crowds out cattails as well as disrupts the life cycles of waterfowl, amphibians, and algae.

The devastating impact that purple loosestrife can have on an area

(courtesy of spinner.cofc.org)

A single plant can release nearly 3 million seeds per year; so one can see how it would be impossible to eradicate this species entirely. Fortunately researchers have discovered a way to biologically control purple loosestrife. There are five known beetles that feed naturally on the plant, including two leaf beetles and three weevils.

  

Over the summer I had the pleasure of meeting a woman by the name of Lisa Tewksbury, who works in the BioControl Lab at the University of Rhode Island. She has worked for years raising Galerucella spp., a beetle that feeds almost solely on purple loosestrife. She begins with a variety of beetles, testing which one feeds the most effectively on the invasive and then raises them by the thousands and releases them into the wild, taking note of their progress in predetermined plots. So far her efforts have been wildly effective, eradicating purple loosestrife almost entirely from the wetlands at the Roger Williams Park Zoo.

In an article by the Michigan Sea Grant, Beetles Take a Bite out of Purple Loosestrife; Native Plants Recover in Some Michigan Wetlands, Gallerucella spp. was responsible for the 100% decline of purple loosestrife in three wetlands. These beetles were released, established populations, and eradicated purple loosestrife from these areas. This study also showed that in the absence of purple loosestrife, native plants were able to recolonize in the wetlands.With people like Lisa Tewskbury and beetles like Galerucella spp. perhaps there is hope on the invasive eradication front.

Bibliography

1. Hamel, Kathy. Non-native Invasive Freshwater Plants. http://www.ecy.wa.gov/programs/wq/plants/weeds/aqua009.html
2. "Lythrum Salicaria." Wikipedia. Wikimedia Foundation, 25 Mar. 2012. Web. 29 Mar. 2012. <http://en.wikipedia.org/wiki/Lythrum_salicaria>.
3. Tewksbury, Lisa et al. 1996-2004. Reestablishment of Native Plants in Roger Williams Park Zoo Wetland, after Biological Control of Purple Loosestrife, Lythrum salicaria.
4. "Michigan Sea Grant News: Beetles Take a Bite out of Purple Loosestrife; Native Plants Recover in some Michigan Wetlands." Michigan Sea Grant: Enhancing the Sustainability of Michigan’s Coastal Communities, Residents, and Businesses through Research, Outreach and Education. 28 May 2003. Web. 15 Apr. 2012.